Latest Papers

ASME Journal of Mechanisms and Robotics

  • Theoretical Analysis of Workspace of a Hybrid Offset Joint
    on December 19, 2024 at 12:00 am

    AbstractOffset joints are widely used in robotics, and literature has demonstrated that axial offset joints can expand the workspace. However, the hybrid offset joint, which incorporates offsets in three orthogonal directions (x, y, and z axes), provides a more flexible and comprehensive range of motion compared to traditional axial offset joints. Therefore, a comprehensive understanding of the workspace of hybrid offset joints with three-directional offsets is essential. First, through a parameter model, the interference motion of hybrid offset joints is studied, considering three different directional offsets and obtaining analytical expressions. Next, based on coordinate transformations, the workspace of this joint is investigated, resulting in corresponding theoretical formulas. In addition, the influence of offset amounts in various directions on the joint’s workspace is examined. Finally, the application of hybrid offset joints in parallel manipulators (PMs) is introduced, highlighting their practical engineering value. Through comparative analysis, it is found that lateral offsets on the x- and y-axes adjust the maximum rotation angles, while the z-axis offset expands the rotational range of these joints. Moreover, by increasing the limit rotation angle of the passive joint in a specific direction, the application of hybrid offset joints in PMs can impact the workspace. These findings offer valuable insights for the design of hybrid offset joints and their applications in robotics.

  • A Novel Delta-Like Parallel Robot With Three Translations and Two Pitch Rotations for Peg-in-Hole Assembly
    on December 19, 2024 at 12:00 am

    AbstractThis paper presents a novel 5-degree-of-freedom (5-DOF) delta-like parallel robot named the double-pitch-delta robot, which can output three translations and two pitch rotations for peg-in-hole assembly. First, the kinematic mechanism of the new robot is designed based on the DOF requirements. Second, the closed-form kinematic model of the double-pitch-delta robot is established. Finally, the workspace of the double-pitch-delta robot is quantitatively analyzed, and a physical prototype of the new robot is developed to verify the effectiveness of the designed mechanism and the established models. Compared with the existing 5-DOF parallel robots with two pitch rotations, the double-pitch-delta robot has a simpler forward displacement model, larger workspace, and fewer singular loci. The double-pitch-delta robot can be also extended as a 6-DOF hybrid robot with the full-cycle tool-axis rotation to satisfy more complex operations. With these benefits, the new robot has a promising prospect in assembly applications.

New Design and Prototype of Two Degrees-of-Freedom Planar Parallel Manipulator for Use in Creating an Infinite 3D Printer

Abstract

This paper presents a novel two degrees-of-freedom planar parallel manipulator (PPM) designed for infinite-axis 3D printing, alongside tools for facilitating future design iterations. Unlike traditional gantry-supported designs used in infinite-axis 3D printing, which impose significant mass movement requirements, the examined new design prioritizes reducing overall weight to enhance speed potential at the cost of a reduced work area. In this innovative approach, the PPM effectively reduces weight by decoupling the motion of the hot end from that of the motor. Motors are attached to the frame, controlling a system of pulleys, and connecting arms to drive the hot-end’s motion. Due to the length of the arms, the hot end will be unable to fully explore the entire printing plane. Verification of the angled PPM for 3D printing involved developing kinematic and dynamic equations, conducting finite element analysis on critical components, and testing a completed prototype. A metaheuristic optimization method was employed to derive optimal design parameters, focusing on optimizing the arm length of the connectors while maximizing dynamic performance. Considerations included the usable workspace and the angle between the connecting arm and end-effector. The final prototype validated the stability and rigidity of the PPM during movement, indicating its viability for 3D printing. The results presented in this paper demonstrate the capabilities of using an angled PPM in infinite 3D printing, providing fundamental knowledge crucial for future designs involving this innovative mechanism.

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